Recently, in a manufacturing process for producing various products such a semiconductor device, liquid crystal display, or optical disk, there has been widely used a sputtering deposition apparatus (referred to as “sputtering apparatus” hereinafter) for depositing a thin film of various types on an object to be treated such as a wafer, glass substrate, polycarbonate substrate, or the like. In such a sputtering apparatus, a predetermined deposited material as a target, which is provided inside a vacuum container, is biased to the cathode beforehand, and ions of discharge gas such as argon (Ar) are collided with the target, whereby the desorbed material of an atom, molecule or cluster, from the material configuring the target, is deposited as a thin film on an object to be treated.
In such a sputtering apparatus, a so-called “magnetron sputtering system” is widely used in order to increase the sputtering speed by increasing the density of plasma obtained by glow discharge in a space in the vicinity of the surface of the target. In the magnetron sputtering system, a magnet unit is provided on the back of the target (the side opposite from the object to be treated), and charged particles are confined in the vicinity of the surface of the target by using a magnetic field generated from the magnet unit, whereby high plasma density is obtained. By increasing the plasma density in this manner, sputtering can be performed at high speed, and the speed of deposition performed on the object to be treated can be increased.
Incidentally, the target in the magnetron sputtering apparatus is a film material, thus the target is naturally scraped and thinned as the object to be treated is processed. Such a phenomenon is caused on the surface of the target facing the object to be treated, and such a phenomenon hardly occurs in the beginning of the use of the target and gradually progresses as the number of processes performed on the object to be treated increases. Therefore, if the usage of the target increases, in other words, if the number of processes performed on the object to be treated increases, the distance between the surface of the target and the object to be treated increases, while the distance between the magnet unit and the surface of the target decreases.
In this manner, if the distances of the surface of the target to the object to be treated and the magnet unit change between the beginning and end of the use of the target, the positional relations of the generated magnetic field to the surface of the target and the object to be treated change, thus the uniformity of the thickness of the film deposited on the object to be treated also changes. Specifically, even if the uniformity of the film thickness is good in the beginning of the use of the target, the problem is that the uniformity of the film thickness worsens in the end of the use of the target. Especially in the case where the object to be treated is a substrate for a liquid crystal display or optical disk, the film thickness is preferably uniform for all products, but if the uniformity deteriorates because of the decrease of the target, the production yield is affected by such phenomenon.
As a method of achieving uniformity of the film thickness in each substrate, for example, there is proposed in Japanese Patent Application Laid-Open No. H10-195649 a technology of forming a uniform film by rotating a magnet by a preset optimum number of rotations in accordance with the material of the target and required quality. Further, Japanese Patent Application Laid-Open No. H8-144058 proposes a technology for forming a uniform film on a rectangular substrate or the like by adjusting a rotation velocity distribution of each of a plurality of magnets. Japanese Patent Application Laid-Open No. 2001-329362 proposes a technology of inhibiting fluctuation of the number of rotations, which is caused by eddy current, and forming a uniform film by using an excellent backing plate material for supporting the target. However, these technologies do not focus on scraping of the target which occurs over time, and thus cannot prevent gradual deterioration of the uniformity of the film thickness in the products which are successively produced between the beginning and end of the use of the target.
As a conventional technology which focuses on such scraping of the target, there are Japanese Patent No. 2912864, Japanese Patent Application Laid-Open No. H9-176852 and Japanese Patent Application Laid-Open No. H10-60640. Specifically, Japanese Patent No. 2912864 and Japanese Patent Application Laid-Open No. H9-176852 are technologies of separating the entire or a part of a permanent magnet unit from a target, and thereby changing the distribution and intensity of a magnetic field on the surface of the target, as well as the position of the magnetic field which is parallel to the target, to secure uniformity of the film thickness from the beginning to the end of the use of the target. Moreover, Japanese Patent Application Laid-Open No. H10-60640 is a technology which is capable of maintaining a fixed film-formation condition by adjusting the exciting electric power to a rotating electromagnetic coil in accordance with the condition of erosion caused on the surface of the target over time.
However, the technologies of Japanese Patent No. 2912864 and Japanese Patent Application Laid-Open No. H9-176852 require not only a mechanism for rotating the permanent magnet unit but also a mechanism for moving the permanent magnet unit up and down to adjust the distance thereof to the target, thus the apparatus becomes complicated and the costs are increased. Moreover, in the technology of the Japanese Patent Application Laid-Open No. H10-60640, provision of the rotating electromagnetic coil complicates the apparatus and increases the costs, and it is extremely troublesome to adjust the exciting electric power to be supplied to the electromagnetic coil to an optimum value.
On the other hand, there are the following difficulties in applying the technologies described in Japanese Patent Application Laid-Open No. H10-195649, Japanese Patent Application Laid-Open No. H8-144058 and Japanese Patent Application Laid-Open No. 2001-329362 to the problem of scraping of the target which occurs over time. Specifically, in Japanese Patent Application Laid-Open No. H10-195649 the number of rotations of the magnet is merely controlled by a fixed number of rotations in accordance with the material and the like of the target, thus even in the case of a target made of the same material, when the distance between the target and the magnet unit or the like is changed because of scraping of the target, increasing unevenness of the film thickness between the products cannot be treated.
Furthermore, in Japanese Patent Application Laid-Open No. H8-144058, it is necessary to provide a plurality of magnets which rotate individually, thus the apparatus becomes complicated and the costs are increased. Also, control is merely performed by adjusting a predetermined rotation velocity distribution of each of the rotating magnets in accordance with the rectangular substrate or the like, thus when the distance between the target and the magnet unit or the like is changed because of scraping of the target, increasing unevenness of the film thickness between the products cannot be treated. Moreover, Japanese Patent Application Laid-Open No. 2001-329362 inhibits fluctuation of the number of rotations of the magnet, which is caused by eddy current, and forms a uniform film by selecting a material for a backing plate, thus the change in the distance between the target and the magnet unit or the like, which us caused by scraping of the target as described, above cannot be treated.
The present invention is therefore contrived in order to solve the problems of the above-described conventional technologies, and an object of the present invention is to provide a sputtering apparatus and method, and a sputtering control program which are configured simply and can secure the uniformity of the film thickness from the beginning to the end of the use of a target.